The present invention relates to a vehicle-onboard signal processing device, for example, a radar system, automobile navigation system, and the like, which is mounted on a vehicle in order to receive and transmit signals between the vehicle and the outside.
In a radio-wave type radar system that uses radio waves of millimeter wave band, the attenuation of radio beam is small even during the bad weather where rain or fog is present, so that the maximum detection distance required for a vehicle-onboard device can be ensured. For this reason, the radio-wave type radar system has been merchandised as a sensor for measuring the distance between the own car and a car ahead or measuring the relative velocity. Such a vehicle-onboard radar system is to be equipped with various magnetic shields to prevent electromagnetic noise from leaking to the outside and also from entering from the outside.
For example, in a device disclosed in Japanese application patent laid-open publication No. Hei 7-66746, a cylindrical shaft made of conductive material is disposed between the inside surface of an outer housing and an internal circuit, and signal lines and the like are placed inside the cylindrical shaft so as to increase the cut-off frequency in the space between the internal circuit and the inside surface of the outer housing and also to block electromagnetic noise generated from the signal lines, and the like.
However, in the prior art, if the signal line connects the external connector placed on the outer housing to the internal circuit, because the signal line is covered with the cylindrical shaft made of conductive material, it is necessary to place the connector at a location on the outer housing that is closest to the internal circuit; as a result, a problem arises because of the limited placement of the connector. This kind of limitation is not preferable for a vehicle-onboard device which already has strict limitations on size and placement. For example, when a vehicle-onboard device is to be mounted in a concave portion of a vehicle, if an external connector is placed at a certain location on the vehicle-onboard device, a problem arises in that an external connection cable cannot be connected to the connector. Even if the external connection cable is connected, the cable may block and prevent the vehicle-onboard device from being mounted in the concave portion. Further, if a cylinder of the appropriate length is properly bent and used instead of the magnetic shielding cylindrical shaft, the connector can be freely placed at any location. However, in this case, a space to place the relatively long, bent cylinder is required in the outer housing, thereby increasing the size of the device.
Furthermore, the foregoing prior art has another problem with electromagnetic noise generated from the signal line leaking from the opening at the end portion of the internal circuit side of the cylindrical shaft, causing insufficient magnetic sealing.
Accordingly, in view of the foregoing problems of the prior art, a first objective of the present invention relating to this application is to provide a vehicle-onboard signal processing device which magnetically shields the transmission line that connects the external connection portion placed on the outer housing to the internal circuit and simultaneously makes it possible to mount the external connection portion at any location without increasing the size of the device.
Furthermore, a second objective of the present invention relating to this application is to provide a vehicle-onboard signal processing device which can perform sufficient magnetic shielding.
A vehicle-onboard signal processing device provided to achieve the first objective to achieve said objectives is mounted on a vehicle so as to receive and transmit a transmission target including a signal and electric power between the vehicle and the outside, and comprises
an internal circuit where said transmission target is input and output,
an outer housing which covers said internal circuit and a conductive shielding layer is applied to the inner-periphery side of said outer housing,
an external connection portion mounted to said outer housing and facing the outside of said outer housing so as to transmit and receive said transmission target with said outside, and
a transmission line which electrically connects said internal circuit to said external connection portion, wherein
said transmission line extends from said external connection portion as a base point, goes between the outer-periphery surface of said outer housing and said shielding layer, extends along the spreading direction of the inner-periphery surface or the outer-periphery surface of the outer housing, penetrates the shielding layer, and then connects to said internal circuit.
Further, a vehicle-onboard signal processing device provided to achieve said second objective is mounted on a vehicle so as to receive and transmit a transmission target including a signal and electric power between the vehicle and the outside, and comprises
an internal circuit board having an internal circuit where said transmission target is input and/or output,
a board support base which supports said internal circuit board,
an outer housing which covers said internal circuit board and said board support base and a conductive shielding layer is applied to the inner-periphery side of said outer housing, and
a transmission line which penetrates said shielding layer from the outer-periphery side to the inner-periphery side and is electrically connected to said internal circuit so as to transmit and receive said transmission target with said outside, wherein
said board support base has a cylindrical shielding portion made of conductive material which covers the outer periphery of the transmission line between the position at which said transmission line penetrates said shielding layer and said internal circuit board;
said internal circuit board comes in contact with said cylindrical shielding portion to close the opening at the end portion of said cylindrical shielding portion;
said internal circuit board has a conductive layer and a noise removal means for removing noise coming through said transmission line; and
the noise removal means is placed immediately before or after the position at which said transmission line extending from said shielding layer penetrates said conductive layer.